[Reversible Cerebral Vasoconstriction Syndrome(RCVS)and Posterior Reversible Encephalopathy Syndrome(PRES)].

Reversible cerebral vasoconstriction syndrome(RCVS)is a clinical and radiological syndrome that is characterized by recurrent severe thunderclap headaches with or without other neurological symptoms and diffuse segmental constriction of cerebral arteries that usually resolves spontaneously within three months. Posterior reversible encephalopathy syndrome(PRES)is also a clinical and radiological syndrome characterized by headache, seizures, altered consciousness, cortical blindness, other focal neurological signs, and a diagnostic imaging picture of brain vasogenic edema. Both syndromes can occur in similar clinical contexts such as hypertension, pre-eclampsia/eclampsia, drug neurotoxicity, uremia, and some autoimmune diseases, and are frequently associated. Although the syndromes are usually fully reversible with early diagnosis and prompt treatment, some cases can develop hemorrhagic or ischemic brain lesions, often resulting in permanent disability. We need to be aware of the typical and atypical imaging manifestations of the syndromes to make an accurate diagnosis.

Arginine is a disease modifier for polyQ disease models that stabilizes polyQ protein conformation.

The polyglutamine (polyQ) diseases are a group of inherited neurodegenerative diseases that include Huntington's disease, various spinocerebellar ataxias, spinal and bulbar muscular atrophy, and dentatorubral pallidoluysian atrophy. They are caused by the abnormal expansion of a CAG repeat coding for the polyQ stretch in the causative gene of each disease. The expanded polyQ stretches trigger abnormal ß-sheet conformational transition and oligomerization followed by aggregation of the polyQ proteins in the affected neurons, leading to neuronal toxicity and neurodegeneration. Disease-modifying therapies that attenuate both symptoms and molecular pathogenesis of polyQ diseases remain an unmet clinical need. Here we identified arginine, a chemical chaperone that facilitates proper protein folding, as a novel compound that targets the upstream processes of polyQ protein aggregation by stabilizing the polyQ protein conformation. We first screened representative chemical chaperones using an in vitro polyQ aggregation assay, and identified arginine as a potent polyQ aggregation inhibitor. Our in vitro and cellular assays revealed that arginine exerts its anti-aggregation property by inhibiting the toxic ß-sheet conformational transition and oligomerization of polyQ proteins before the formation of insoluble aggregates. Arginine exhibited therapeutic effects on neurological symptoms and protein aggregation pathology in Caenorhabditis elegans, Drosophila, and two different mouse models of polyQ diseases. Arginine was also effective in a polyQ mouse model when administered after symptom onset. As arginine has been safely used for urea cycle defects and for mitochondrial myopathy, encephalopathy, lactic acid and stroke syndrome patients, and efficiently crosses the blood-brain barrier, a drug-repositioning approach for arginine would enable prompt clinical application as a promising disease-modifier drug for the polyQ diseases.

Expansions of intronic TTTCA and TTTTA repeats in benign adult familial myoclonic epilepsy.

Epilepsy is a common neurological disorder, and mutations in genes encoding ion channels or neurotransmitter receptors are frequent causes of monogenic forms of epilepsy. Here we show that abnormal expansions of TTTCA and TTTTA repeats in intron 4 of SAMD12 cause benign adult familial myoclonic epilepsy (BAFME). Single-molecule, real-time sequencing of BAC clones and nanopore sequencing of genomic DNA identified two repeat configurations in SAMD12. Intriguingly, in two families with a clinical diagnosis of BAFME in which no repeat expansions in SAMD12 were observed, we identified similar expansions of TTTCA and TTTTA repeats in introns of TNRC6A and RAPGEF2, indicating that expansions of the same repeat motifs are involved in the pathogenesis of BAFME regardless of the genes in which the expanded repeats are located. This discovery that expansions of noncoding repeats lead to neuronal dysfunction responsible for myoclonic tremor and epilepsy extends the understanding of diseases with such repeat expansion.

Characteristic microglial features in patients with hereditary diffuse leukoencephalopathy with spheroids.

OBJECTIVE: To clarify the histopathological alterations of microglia in the brains of patients with hereditary diffuse leukoencephalopathy with spheroids (HDLS) caused by mutations of the gene encoding the colony stimulating factor-1 receptor (CSF-1R). METHODS: We examined 5 autopsied brains and 1 biopsy specimen from a total of 6 patients with CSF-1R mutations. Detailed immunohistochemical, biochemical, and ultrastructural features of microglia were examined, and quantitative analyses were performed. RESULTS: In layers 3 to 4 of the frontal cortex in HDLS brains, microglia showed relatively uniform and delicate morphology, with thin and winding processes accompanying knotlike structures, and significantly smaller areas of Iba1 immunoreactivity and lower numbers of Iba1-positive cells were evident in comparison with control brains. On the other hand, in layers 5 to 6 and the underlying white matter, microglia were distributed unevenly; that is, in some areas they had accumulated densely, whereas in others they were scattered. Immunoblot analyses of microglia-associated proteins, including CD11b and DAP12, revealed that HDLS brains had significantly lower amounts of these proteins than diseased controls, although Ki-67-positive proliferative microglia were not reduced. Ultrastructurally, the microglial cytoplasm and processes in HDLS showed vesiculation of the rough endoplasmic reticulum and disaggregated polyribosomes, indicating depression of protein synthesis. On the other hand, macrophages were immunonegative for GLUT-5 or P2ry12, indicating that they were derived from bone marrow. INTERPRETATION: The pathogenesis of HDLS seems to be associated with microglial vulnerability and morphological alterations. Ann Neurol 2016;80:554-565.

A mutation of COX6A1 causes a recessive axonal or mixed form of Charcot-Marie-Tooth disease.

Charcot-Marie-Tooth disease (CMT) is the most common inherited neuropathy characterized by clinical and genetic heterogeneity. Although more than 30 loci harboring CMT-causing mutations have been identified, many other genes still remain to be discovered for many affected individuals. For two consanguineous families with CMT (axonal and mixed phenotypes), a parametric linkage analysis using genome-wide SNP chip identified a 4.3 Mb region on 12q24 showing a maximum multipoint LOD score of 4.23. Subsequent whole-genome sequencing study in one of the probands, followed by mutation screening in the two families, revealed a disease-specific 5 bp deletion (c.247-10_247-6delCACTC) in a splicing element (pyrimidine tract) of intron 2 adjacent to the third exon of cytochrome c oxidase subunit VIa polypeptide 1 (COX6A1), which is a component of mitochondrial respiratory complex IV (cytochrome c oxidase [COX]), within the autozygous linkage region. Functional analysis showed that expression of COX6A1 in peripheral white blood cells from the affected individuals and COX activity in their EB-virus-transformed lymphoblastoid cell lines were significantly reduced. In addition, Cox6a1-null mice showed significantly reduced COX activity and neurogenic muscular atrophy leading to a difficulty in walking. Those data indicated that COX6A1 mutation causes the autosomal-recessive axonal or mixed CMT.

[Hereditary diffuse leukoencephalopathy with spheroids (HDLS): a review of the literature on its clinical characteristics and mutations in the colony-stimulating factor-1 receptor gene].

Hereditary diffuse leukoencephalopathy with spheroids (HDLS) is an early-onset dementia that predominantly affects the cerebral white matter. After the discovery of a gene encoding the colony stimulating factor 1 receptor (CSF-1R) as a causative gene in patients with HDLS, gene analysis of CSF-1R enabled the diagnosis of HDLS without histopathological evidence. To clarify the genetic and clinical characteristics of HDLS, here, we reviewed the characteristics of patients with HDLS with CSF-1R mutations in the literature. Seventy-three patients from 54 pedigrees with HDLS from various ethnic backgrounds have been reported. Among them, Japanese patients account for 22% (16 patients from 15 pedigrees). Mean age at onset was 45 years (18 to 78 years). A wide range of clinical features including cognitive decline, behavioral changes, seizures, pyramidal signs, and parkinsonism have been described in these patients. Various kinds of mutations were found in the tyrosine kinase domain of CSF-1R. A frameshift mutation causing nonsense-mediated mRNA decay was also described. This suggests that haploinsufficiency of CSF-1R is sufficient to cause HDLS. Neuropathological analysis revealed that microglia in the brains of patients demonstrated distinct morphology and distribution. These results suggest that primary microglial dysfunction due to CSF-1R signaling perturbation may underlie the pathogenesis of HDLS.

Haploinsufficiency of CSF-1R and clinicopathologic characterization in patients with HDLS.

OBJECTIVE: To clarify the genetic, clinicopathologic, and neuroimaging characteristics of patients with hereditary diffuse leukoencephalopathy with spheroids (HDLS) with the colony stimulating factor 1 receptor (CSF-1R) mutation. METHODS: We performed molecular genetic analysis of CSF-1R in patients with HDLS. Detailed clinical and neuroimaging findings were retrospectively investigated. Five patients were examined neuropathologically. RESULTS: We found 6 different CSF-1R mutations in 7 index patients from unrelated Japanese families. The CSF-1R mutations included 3 novel mutations and 1 known missense mutation at evolutionarily conserved amino acids, and 1 novel splice-site mutation. We identified a novel frameshift mutation. Reverse transcription PCR analysis revealed that the frameshift mutation causes nonsense-mediated mRNA decay by generating a premature stop codon, suggesting that haploinsufficiency of CSF-1R is sufficient to cause HDLS. Western blot analysis revealed that the expression level of CSF-1R in the brain from the patients was lower than from control subjects. The characteristic MRI findings were the involvement of the white matter and thinning of the corpus callosum with signal alteration, and sequential analysis revealed that the white matter lesions and cerebral atrophy relentlessly progressed with disease duration. Spotty calcifications in the white matter were frequently observed by CT. Neuropathologic analysis revealed that microglia in the brains of the patients demonstrated distinct morphology and distribution. CONCLUSIONS: These findings suggest that patients with HDLS, irrespective of mutation type in CSF-1R, show characteristic clinical and neuroimaging features, and that perturbation of CSF-1R signaling by haploinsufficiency may play a role in microglial dysfunction leading to the pathogenesis of HDLS.

Coexistence of Huntington's disease and amyotrophic lateral sclerosis: a clinicopathologic study.

We report a retrospective case series of four patients with genetically confirmed Huntington's disease (HD) and sporadic amyotrophic lateral sclerosis (ALS), examining the brain and spinal cord in two cases. Neuropathological assessment included a polyglutamine recruitment method to detect sites of active polyglutamine aggregation, and biochemical and immunohistochemical assessment of TDP-43 pathology. The clinical sequence of HD and ALS varied, with the onset of ALS occurring after the mid-50's in all cases. Neuropathologic features of HD and ALS coexisted in both cases examined pathologically: neuronal loss and gliosis in the neostriatum and upper and lower motor neurons, with Bunina bodies and ubiquitin-immunoreactive skein-like inclusions in remaining lower motor neurons. One case showed relatively early HD pathology while the other was advanced. Expanded polyglutamine-immunoreactive inclusions and TDP-43-immunoreactive inclusions were widespread in many regions of the CNS, including the motor cortex and spinal anterior horn. Although these two different proteinaceous inclusions coexisted in a small number of neurons, the two proteins did not co-localize within inclusions. The regional distribution of TDP-43-immunoreactive inclusions in the cerebral cortex partly overlapped with that of expanded polyglutamine-immunoreactive inclusions. In the one case examined by TDP-43 immunoblotting, similar TDP-43 isoforms were observed as in ALS. Our findings suggest the possibility that a rare subset of older HD patients is prone to develop features of ALS with an atypical TDP-43 distribution that resembles that of aggregated mutant huntingtin. Age-dependent neuronal dysfunction induced by mutant polyglutamine protein expression may contribute to later-life development of TDP-43 associated motor neuron disease in a small subset of patients with HD.

Aprataxin, causative gene product for EAOH/AOA1, repairs DNA single-strand breaks with damaged 3'-phosphate and 3'-phosphoglycolate ends.

Aprataxin is the causative gene product for early-onset ataxia with ocular motor apraxia and hypoalbuminemia/ataxia with oculomotor apraxia type 1 (EAOH/AOA1), the clinical symptoms of which are predominantly neurological. Although aprataxin has been suggested to be related to DNA single-strand break repair (SSBR), the physiological function of aprataxin remains to be elucidated. DNA single-strand breaks (SSBs) continually produced by endogenous reactive oxygen species or exogenous genotoxic agents, typically possess damaged 3'-ends including 3'-phosphate, 3'-phosphoglycolate, or 3'-alpha, beta-unsaturated aldehyde ends. These damaged 3'-ends should be restored to 3'-hydroxyl ends for subsequent repair processes. Here we demonstrate by in vitro assay that recombinant human aprataxin specifically removes 3'-phosphoglycolate and 3'-phosphate ends at DNA 3'-ends, but not 3'-alpha, beta-unsaturated aldehyde ends, and can act with DNA polymerase beta and DNA ligase III to repair SSBs with these damaged 3'-ends. Furthermore, disease-associated mutant forms of aprataxin lack this removal activity. The findings indicate that aprataxin has an important role in SSBR, that is, it removes blocking molecules from 3'-ends, and that the accumulation of unrepaired SSBs with damaged 3'-ends underlies the pathogenesis of EAOH/AOA1. The findings will provide new insight into the mechanism underlying degeneration and DNA repair in neurons.

Long-term therapeutic efficacy and safety of low-dose tacrolimus (FK506) for myasthenia gravis.

OBJECTIVE: To elucidate the long-term therapeutic efficacy and safety of low-dose FK506 (tacrolimus) in patients with myasthenia gravis (MG). PATIENTS AND METHODS: We treated nine patients with MG (all women: age range: 35-83 years (mean: 51.1 years); MGFA classification: 4 type IIa, 4 type IIb, and 1 type IVb patients) with FK506 for more than 24 months (observation period: 24-46 months). All the patients had undergone extended thymectomy before FK506 treatment; two patients (22.2%) had noninvasive thymoma and six (66.7%) had thymic hyperplasia. We evaluated total Quantitative MG (Q-MG) score, anti-acetylcholine receptor (AChR) antibody titer in the blood, interleukin 2 (IL-2) production in peripheral blood mononuclear cells (PBMCs), administration dosage of prednisolone (PSL), and adverse effects of FK506. RESULTS: A reduction in steroid dosage of 50% without worsening of the symptoms was observed 1 year after FK506 administration in three out of six steroid-dependent MG patients (50.0%). The total Q-MG scores (range: 0-39 points) at 6 months and 1 year after FK506 administration improved by 3 points or more in six (66.7%) and seven (77.8%) out of nine patients, respectively. The efficacy of FK506 was maintained for more than 2 years. Although adverse effects were observed in three patients (33.3%), these were not serious. CONCLUSIONS: Our study indicates that low-dose FK506 treatment may be efficacious not only in controlling intractable myasthenic symptoms, but also in reducing steroid dosage, and that FK506 is safe as an adjunctive drug to PSL for MG treatment for a maximum of 3 years.